Plasma antennas are being considered for use in many different industrial fields. A plasma antenna is a type of radio antenna in which plasma is used instead of the metal elements of a traditional antenna. A plasma antenna can be used for both transmission and reception. Early practical examples of the technology used discharge tubes to contain the plasma and are referred to as ionized gas plasma antennas. Ionized gas plasma antennas can be turned on and off and are good for stealth and resistance to electronic warfare and cyber-attacks. Ionized gas plasma antennas can be nested such that the higher frequency plasma antennas are placed inside lower frequency plasma antennas. Higher frequency ionized gas plasma antenna arrays can transmit and receive through lower frequency ionized gas plasma antenna arrays. This means that the ionized gas plasma antennas can be co-located and ionized gas plasma antenna arrays can be stacked. Ionized gas plasma antennas can eliminate or reduce co-site interference. Smart ionized gas plasma antennas use plasma physics to shape and steer the antenna beams without the need of phased arrays. Satellite signals can be steered and/or focused in the reflective or refractive modes using banks of plasma tubes making unique ionized gas satellite plasma antennas. The thermal noise of ionized gas plasma antennas is less than in the corresponding metal antennas at the higher frequencies. Solid state plasma antennas (also known as plasma silicon antennas) with steerable directional functionality that can be manufactured using standard silicon chips are now also in development.
Phased array antennas are disclosed in U.S. Pat. No. 4,905,014 issued to Gonzalez et al. In general, a microwave phasing structure includes a support matrix, i.e., a dielectric substrate, and a reflective means, i.e., a ground plane, for reflecting microwaves within the frequency-operating band. The reflective means is supported by a support matrix. An arrangement of electromagnetically loading structures is supported by the support matrix at a distance from the reflective means, which can be less than a fraction of the wavelength of the highest frequency in the operating frequency range. The electromagnetically loading structures are dimensioned, oriented, and interspaced from each other and disposed at a distance from the reflective means, as to provide the emulation of the desired reflective surface of selected geometry. Specifically, the electromagnetically-loading structures form an array of metallic patterns, each metallic pattern preferably being in the form of a cross, i.e., X configuration. It is disclosed that each electromagnetically-loading structure can be constructed to form different geometrical patterns and, in fact, could be shorted crossed dipoles, metallic plates, irises, apertures, etc. It is further disclosed that the microwave phasing structures of Gonzalez et al. (014) patent may be used for electromagnetically emulating a desired microwave-focusing element of a selected geometry.
The selected geometry of the desired reflective surface can be a parabolic surface in order to emulate a parabolic reflector wherein all path lengths of the reflected incident electromagnetic waves are equalized by phase shifting affected by the microwave phasing structure of the present disclosure. While the microwave phasing structure may emulate desired reflective surfaces of selected geometries such as a parabola, the microwave phasing structure is generally flat in shape. However, the shape of the microwave phasing structure may be conformal to allow for mounting on substantially non-flat surfaces.
U.S. Pat. No. 7,474,723 (Pavliscak) discloses a gas plasma antenna with a rigid, flexible, or semi-flexible substrate and an improved method of generating a uniform electron density. The antenna has a plasma display panel (PDP) containing a multiplicity of Plasma-shells, each Plasma-shell containing a gas which is ionized to produce electron density. Each Plasma-shell acts alone or in concert with other Plasma-shells to form a dipole or pattern of dipoles. In a phased array plasma antenna characterized by a plurality of localized gas discharge areas, each gas area is selectively and sufficiently ionized to form a reflector to incident radiation, the improvement wherein: each localized gas discharge area is confined within a gas encapsulating Plasma-shell, each Plasma-shell affixed to a substrate, at least two or more electrodes in contact with each gas encapsulating Plasma-shell, said electrodes being affixed to or embedded within the substrate, and AC electronic circuitry including address and sustain waveform electronics for addressing and sustaining the electrodes so as to selectively ionize a gas within a Plasma-shell and produce a controllable level of electron density over time within each Plasma-shell, each Plasma-shell acting alone or in concert with other Plasma-shells to form dipoles or patterns of dipoles.
U.S. Pat. No. 5,963,169 (Anderson) describes an antenna in which electromagnetic signals in the High Frequency and Super High Frequency bands are propagated utilizing ionized gas, or plasma. Energized electrodes ionize the gas and the plasma is confined within non-metallic coaxial tubes contained within a non-metallic pressure vessel. Electric field gradients are used to change the shape and density of the plasma to affect the gain and directivity of the antenna. The inner plasma tube acts as the radiating source, while the outer plasma tube is used to change the radiation of the inner tube and to reflect the radiated signal. Instrumentation measures the density of the plasma providing a means to measure incoming signals as well as to regulate the radiation frequency.
Published U.S. Patent Document 20030142021 Anderson) describes an antenna system and method for a plurality of plasma antennas driven by means of an optical driver. In one embodiment the driver comprises one or more lasers which may be modulated by one or more electro-optical modulators to produce a modulated laser signal. The modulated laser signal may be supplied to the plasma antenna by optical fibers whereby the photons from the modulated signal impart momentum to the plasma particles. The plasma particles, which may include unbound electrons, oscillate in accord with the modulated laser signal to radiate electromagnetic energy. In one embodiment, the plasma antenna is operated at a frequency near the resonant frequency of the plasma to form a more efficient radiator requiring a smaller size than to a metallic antenna. In another embodiment a plurality of closely spaced plasma antennas are operated with different plasma resonant frequencies such that one plasma antenna is electrically invisible with respect to another plasma antenna.
In an ionized gas plasma antenna, a gas is ionized to create a plasma. Unlike gases, plasmas have very high electrical conductivity so it is possible for radio frequency signals to travel through them so that they act as a driven element (such as a dipole antenna) to radiate radio waves, or to receive them. Alternatively the plasma can be used as a reflector or a lens to guide and focus radio waves from another source. Solid-state antennas differ in that the plasma is created from electrons generated by activating thousands of diodes on a silicon chip.
Commonly assigned U.S. Provisional Patent Application U.S. Ser. No. 61/767,059 (Schill, filed 13 Mar. 2013) describes, amongst other technology, a plasma generating system that can be used, among other purposes, to enable practice of the present technology by generating the plasma field containing information camouflaged therein. That reference, and all references cited herein, are incorporated in their entirety herein.
That technology relates to the fact that a simple nonlinear theory has been developed to capture the essence and process of electron channeling for an energetic electron beam passing through a cool plasma. In this model, the electron species is separated into two different species of the same type but with very different initial particle states immersed in a sea of nearly stationary ions. Under appropriate conditions, theory suggests that the fast moving secondary electron emission particles passing through a discharge may be responsible for a non-arc-like plasma pinch effect that results in experiments with periodic pulse discharge. In certain periodic pulsed plasma discharge experiments, it has been observed that under specific conditions a plasma glow discharge column is generated and tends to seek the central location of the discharge electrodes away from the electrode edges and chamber walls. Further, the column appears to have the properties of a stabilized equilibrium plasma pinch in a glow (non-arc-like) state. This is unusual since, normally field enhancements occur on edges of the electrode resulting in arc-like discharge breakdown. Also, the column of plasma that protrudes from the anode emits highly intense, non-uniform light that is uncharacteristically bright for a typical glow discharge with the same applied voltage. It appears that under certain conditions and assumptions, the secondary electron beam will initiate and sustain electron channeling and subsequent pinch forces due to charge repulsion, charge neutralization, and self-magnetic forces. This theory can be expanded beyond a glow discharge and be applied to any moderately energetic beam that passes through plasma, as long as the assumptions and conditions are not violated. An apparatus was also constructed to investigate this phenomenon. It delivers controlled pulses that generate stable and repetitive pinched discharges. It allows the user to change the parameters and the conditions of the discharge and to study the conditions that bring about plasma constriction. Measurement tools were integrated into the system including current and voltage probes and image analysis tools. Based on the models developed and on experimental implications, a parameter space based on the properties of the discharge has been identified that leads to the pinch of the discharge. Further, from transient discharge measurements, various properties of the pinch have been identified.